This research program will define factors which modify protein turnover in lung tissue and in specific cell types of the lung parenchyma. The experimental approach involves in vivo studies of lung growth following pneumonectomy and in vitro studies of isolated perfused lungs and suspensions of freshly isolated Type II cells. Methodology will be developed to allow measurements of protein synthesis and degradation in these preparations. Effects of hormonal, metabolic and other factors on the turnover of lung proteins will be defined and localized to specific steps in the pathway of turnover. These steps include the transport and intracellular supply of amino acids, charging of aminoacyl-tRNA, tissue stores of high-energy phosphates, and reactions of the ribosome cycle including peptide-chain initiation and elongation. Regulation of protein turnover in lung tissue will be compared to that in Type II alveolar epithelial cells where proper development and metabolism are required to maintain normal pulmonary structure and function. Other studies will attempt to identify a suitable specific protein whose turnover could be measured in lung tissue and in Type II cells. Factors affecting this turnover will be investigated. These experiments will contribute to knowledge of normal lung biochemistry and thus to the elucidation of the mechanisms of pulmonary disease.